21521252501 has 16 divisors (see below), whose sum is σ = 25427800320. Its totient is φ = 17829331200.

The previous prime is 21521252491. The next prime is 21521252509. The reversal of 21521252501 is 10525212512.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21521252501 - 2²² = 21517058197 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21521252509) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 236036 + ... + 314253.

It is an arithmetic number, because the mean of its divisors is an integer number (1589237520).

Almost surely, 2^21521252501 is an apocalyptic number.

It is an amenable number.

21521252501 is a deficient number, since it is larger than the sum of its proper divisors (3906547819).

21521252501 is a wasteful number, since it uses less digits than its factorization.

21521252501 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 550484.

The product of its (nonzero) digits is 2000, while the sum is 26.

The spelling of 21521252501 in words is "twenty-one billion, five hundred twenty-one million, two hundred fifty-two thousand, five hundred one".